EGR is a known method for reducing NOx emissions in internal combustion engines. A conventional EGR system works by taking a by-pass stream of engine exhaust gas from an engine exhaust manifold and directing it back into the engine for combustion. Typically, the exhaust gas stream is first pressurized a desired amount for injection into the engine's induction system. It is also mixed with intake air and a combustion fuel mixture for subsequent combustion. A control valve can be included in the EGR system to regulate the amount of exhaust gas that is routed to the engine induction system based on engine demand. The process of recirculating the exhaust gas insures that partially oxidized NOx exiting the engine becomes fully oxidized, thereby reducing smog producing partially oxidized NOx engine emissions.
EGR systems are used in conjunction with turbocharged gasoline and diesel-powered internal combustion engines. In such turbocharged systems, exhaust gas existing the engine is directed to a turbine housing of a turbocharger to turn a turbine wheel that is rotatably mounted therein. The exhaust gas exists the turbine housing, and an EGR bypass exhaust stream is taken for the purpose of being introduced into the engine's intake system for subsequent combustion. A control valve can be used to regulate the amount of the EGR bypass exhaust stream taken for this purpose.
The EGR exhaust stream is directed to an inlet opening of a turbocharger compressor housing that includes a compressor impeller that is rotatably disposed therein. The compressor impeller is connected to the turbine wheel via a common shaft, and is rotating from the passage of the exhaust gas through the turbine housing. As the EGR exhaust gas passes through the compressor housing the compressor impeller operates to pressurize the exhaust gas so that it exits the compressor housing at a desired boost pressure for subsequent introduction into the engine intake system, mixing with a combustion fuel mixture, and ultimately combustion within the engine.
A problem that exists with such conventional turbocharger engines comprising EGR systems relates to the introduction of the EGR exhaust gas into the compressor housing and the fact that such EGR exhaust gas flow is known to include particulate matter. The presence of such particular matter within the EGR exhaust gas flow can cause severe damage the turbocharger compressor impeller, e.g., by eroding and/or impacting the leading edges of the compressor impeller, which can reduce the performance of the compressor over time thereby reducing turbocharger efficiency and engine performance.
It is, therefore, desired that a device be constructed for use with an EGR system that is capable of minimizing and/or eliminating all together the particulate matter within an EGR exhaust gas system. It is also desirable that such device be configured to perform this function in a manner that facilitates use with a turbocharger engine system, and that further does so without creating a pressure drop within the system that could adversely impact turbocharger and engine performance.